Composite Hemiface/Calvarium Allograft Transplantation Model in the Rat

The purpose of this study was to extend the application of the face/scalp allograft transplantation model in rats by incorporation of the scalp, calvarial bone, and facial skin in a single surgical procedure based on the same vascular pedicle as a new treatment option for extensive craniofacial deformities with large bone defects.

Seven transplantations were performed across the MHC barrier between Lewis-Brown Norway (LBN, RT1l + n) and Lewis (LEW, RT1l) rats under a tapered dose of cyclosporine A monotherapy. Calvarial bone and face flap were dissected on the same pedicle of the common carotid artery and external jugular vein and were transplanted to the deepithelialized recipient faces. Flap angiography was used to demonstrate the blood supply of the vascularized calvarial bone grafts. Daily physical examination, bone histology, and CT scans were used to evaluate the persistence of the bone structure over time. Flow cytometry was used to evaluate donor-specific chimerism for MHC class I - RT1n-specific antigens.

No signs of rejection or bone resorption were noted up to an average 150 days post transplant with the longest follow-up of 220 days, and animals are still under observation. Bone histology revealed viable bone and bone marrow structure at 105 days post transplant. CT scan showed intact bone grafts up to 105 days. At day 100, post transplant chimerism level showed 2.1% for CD4/R1n, 2.2% for CD8/RT1n T-cell subpopulation, and 3.5% for CD45RA/RT1n of B lymphocytes.

The authors presented a composite face/scalp allograft transplantation model in which vascularized calvarial bone graft was included for reconstruction of bone defects. Proper tolerance was induced across the MHC barrier under a low-dose CsA monotherapy protocol with the presence of donor-specific chimerism in the peripheral blood.